1.1 Estimate, round, & manipulate very large…numbers. Number Sense Sense.

1.1 Estimate, round, & manipulate1.1 Estimate, round, & manipulatevery large…numbers.very large…numbers.

NumberNumber

SenseSense

1.5 Identify & represent on a 1.5 Identify & represent on a number line…positive integers.number line…positive integers.

NumberNumber

SenseSenseFifthFifth

GradeGrade

2.3 Use a variety of methods, 2.3 Use a variety of methods, such as numbers…and models such as numbers…and models

to explain mathematical to explain mathematical reasoning.reasoning.

MathematicalMathematical

ReasoningReasoningFifthFifth

GradeGrade

ObjectivesObjectives

To be able to round numbers to the To be able to round numbers to the nearest tennearest ten

To be able to round numbers to the To be able to round numbers to the nearest hundrednearest hundred

To be able to round numbers to the To be able to round numbers to the nearest thousandnearest thousand

VocabularyVocabulary

Round – to replace an exact number by Round – to replace an exact number by another that is close to it in value and another that is close to it in value and easier to use. For example, 52, rounded easier to use. For example, 52, rounded to the nearest ten is 50.to the nearest ten is 50.

Use roundingUse rounding• When the question asks you

to estimate.• When the question asks

“about how many”…?• When an exact answer isn’t

possible.• When an answer is difficult to obtain.

Memorize this PoemMemorize this PoemFind the place value.Look right next door.4 or less just ignore.5 or more, add 1 more.Sweep the numbers to the right off the floor.Change them to zeros forevermore.

Round this number to the nearestRound this number to the nearestten.ten.

Find the place value.4 7

Circle the number in the ten’s place.


Look right next door.

4 7Draw an arrow to the right of the

number.


4 or less, just ignore.

4 77 is larger than 4 so go to the

next line of the poem.


5 or more, add 1 more.

4 7Add 1 to the 4.

+1

Round Round thisthis number to the nearest number to the nearestten.ten.

Sweep the numbers to the right off the floor. 5 7

After adding 1 to the 4, remove all thenumbers to the right of the

ten’s place.

Round Round thisthis number to the nearest number to the nearestten.ten.

Change them to zeros forevermore.

5 7Put a zero in its place.

0

The AnswerThe Answer

4 7 rounded to the nearest ten’s place is

5 040 5047

Note 47 is closer to 50 on the number line.

Round this number to the nearestRound this number to the nearesthundred.hundred.

Find the place value.9 8 6

Circle the number in the hundred’s place.



9 8 6Draw an arrow to the right of the

hundred’s place.



9 8 68 is larger than 4 so go to the

next line of the poem.



9 8 6Add 1 to the 9.

+1


Sweep the numbers to the right off the floor. 1, 0 8 6After adding 1 to the 9, remove the

numbers to the right of the hundred’splace.



1, 0 8 6Put zeros in their place.

0 0

The AnswerThe Answer986 rounded to the nearest hundred’s

place is1, 0 0 0

1,000900 986

Note 986 is closer to 1,000 on the number line.

Round this number to the nearestRound this number to the nearestten thousand.ten thousand.

Find the place value.

3 6 8,9 7 1Circle the number in the ten

thousand’s place.



3 6 8,9 7 1

Draw an arrow to the right of the number.



3 6 8,9 7 1

8 is larger than 4 so go to the nextline of the poem.



3 6 8,9 7 1Add 1 to the ten thousand’s place value.

+1


Sweep the numbers to the right off the floor.3 7 8,9 7

1After adding 1 to the 6, remove all thenumbers to the right of the

ten thousand’s place.



3 7 8,9 7 1Put zeros in their place.

0,0 0 0


368,971 rounded to the nearest ten thousand is3 7 0,0 0

0360,000 370,000368,971

Note 368,971 is closer to 370,000 on the number line.

Round this number to the nearestRound this number to the nearestthousand.thousand.


3 5, 3 2 7Circle the number in the thousand’s

place.



3 5, 3 2 7Draw an arrow to the right of the

number.



3 5, 3 2 7

Since 3 is less than 4 we do not changethe 5.


Sweep the numbers to the right off the floor.3 5, 3 2 7

Remove all the numbers to theright of the thousand’s place.



3 5, 3 2 7

Put zeros in their place.

0 0 0

AnswerAnswer35,327 rounded to the

nearest thousand is

3 5, 0 0 035,000 36,00035,327


Round this number to the nearestRound this number to the nearestdollar.dollar.


$ 5. 8 7

Circle the number where the dollarsare.



$ 5. 8 7

Draw an arrow to the right of thecircled number.



$ 5. 8 78 is greater than 4 so go to the next

line of the poem.



$ 5. 8 7Since 8 is greater than 5 add 1 to the

dollar place value.

+1


Sweep the numbers to the right off the floor. $ 6. 8 7After changing the 5 to a 6, remove

the numbers to the right of the dollar.



$ 6. 8 7Put zeros in their place.

0 0


$5.87 rounded to the

nearest dollar is$ 6. 0 0$5.00 $6.00$5.87

Note $5.87 is closer to $6.00 on the numberline.

Round this number to the nearestRound this number to the nearesttenth place.tenth place.


4. 8 7 1Circle the number in the tenth’s place.



4. 8 7 1Draw an arrow to the right of the

circled number.


4 or less just ignore.

4. 8 7 18 is greater than 4 so go to the next

line of the poem.



4. 8 7 1Since 7 is greater than 5, add 1 to the

tenth’s place.

+1


Sweep the numbers to the right off the floor. 4. 9 7 1Remove the numbers to the right of

the tenth’s place value.



4. 9 7 1With decimals you don’t have to

add zeros to the right.


4.871 rounded to the nearest tenth place is4. 94.8 4.94.871

Note 4.871 is closer to 4.9 on the numberline.

Here’s Another StrategyHere’s Another Strategy

The Clothesline Approach

Step 1 – Read the problem carefully.Step 1 – Read the problem carefully.

Round this number to the nearestthousand.

7,790

Step 2 – Circle the place value you are Step 2 – Circle the place value you are rounding torounding to


7,790

Step 2 – Write down the Step 2 – Write down the thousandthousand on on either side of this numbereither side of this number


7,7907,000 8,000

Step 3 – Put the smallest number on the Step 3 – Put the smallest number on the left pole and the largest on the right.left pole and the largest on the right.


7,7907,000 8,0007,000 8,000

Step 4 – Think where your number Step 4 – Think where your number would go between these poles.would go between these poles.Round this number to the nearest

thousand.

7,7907,000 8,000

Now think! 7,500 wouldgo right in the middle.

7,500

Step 5 – Hang your number where you Step 5 – Hang your number where you think it should go.think it should go.


7,7907,000 8,000

7,500 7,790

Step 6 – The pole you are closest to is Step 6 – The pole you are closest to is your answer.your answer.


7,7907,000 8,000

7,500 7,790


7,790 rounded to the nearest thousand is

8,0007,000 8,0007,790


Round these numbers to the Round these numbers to the nearest ten.nearest ten.

1 3 9

4 5

2 8 2

9 7

1 4 0

5 0

2 8 0

1 0 0

Round these numbers to the Round these numbers to the nearest hundred.nearest hundred.

2, 1 3 9

1 9, 7 4 5

2 8 2

3, 1 9 7

2, 1 0 0

1 9, 7 0 0

3 0 0

3, 2 0 0

Round these numbers to the Round these numbers to the nearest thousand.nearest thousand.

2, 8 3 9

1 9, 4 4 5

8, 9 8 2

4 3,1 9 7

3, 0 0 0

1 9, 0 0 0

9, 0 0 0

4 3, 0 0 0

CreditsCredits

Clipart from “Microsoft Clip Gallery” located on the Internet at http://cgl.microsoft.com/clipgallerylive/default.asp •Clipart from ClickArt 125,000 DeluxeImage Pak, T/Maker Co., BroderbundSoftware, Inc.

1.1 Estimate, round, & manipulate very large…numbers. Number Sense Sense.

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